A solid oxide fuel cell (hereinafter, SOFC) as a fuel cell is widely known as a highly efficient fuel cell having wide use. Such an SOFC has a high operating temperature in order to increase ionic conductivity. Thus, air that has been expelled from a compressor of a gas turbine is usable as the air supplied to an air electrode (as an oxidant). Also, the SOFC enables high-temperature fuel that has been unusable to be used as fuel for a combustor of the gas turbine.
Thus, for example, as described in the below-listed Patent Literature 1, various combinations of an SOFC, a gas turbine, and a steam turbine have been proposed as a power generation system that achieves high power generation efficiency. The combined system described in Patent Literature 1 is provided with an SOFC, a gas turbine combustor that combusts exhaust fuel gas and exhaust air expelled from the SOFC, and a gas turbine having a compressor that compresses air for supply to the SOFC.